git-commit-vandalism/Documentation/git-difftool.txt
Tao Klerks 42943b950e mergetool: new config guiDefault supports auto-toggling gui by DISPLAY
When no merge.tool or diff.tool is configured or manually selected, the
selection of a default tool is sensitive to the DISPLAY variable; in a
GUI session a gui-specific tool will be proposed if found, and
otherwise a terminal-based one. This "GUI-optimizing" behavior is
important because a GUI can make a huge difference to a user's ability
to understand and correctly complete a non-trivial conflicting merge.

Some time ago the merge.guitool and diff.guitool config options were
introduced to enable users to configure both a GUI tool, and a non-GUI
tool (with fallback if no GUI tool configured), in the same environment.

Unfortunately, the --gui argument introduced to support the selection of
the guitool is still explicit. When using configured tools, there is no
equivalent of the no-tool-configured "propose a GUI tool if we are in a GUI
environment" behavior.

As proposed in <xmqqmtb8jsej.fsf@gitster.g>, introduce new configuration
options, difftool.guiDefault and mergetool.guiDefault, supporting a special
value "auto" which causes the corresponding tool or guitool to be selected
depending on the presence of a non-empty DISPLAY value. Also support "true"
to say "default to the guitool (unless --no-gui is passed on the
commandline)", and "false" as the previous default behavior when these new
configuration options are not specified.

Signed-off-by: Tao Klerks <tao@klerks.biz>
Acked-by: David Aguilar <davvid@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-04-05 21:03:29 -07:00

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git-difftool(1)
===============
NAME
----
git-difftool - Show changes using common diff tools
SYNOPSIS
--------
[verse]
'git difftool' [<options>] [<commit> [<commit>]] [--] [<path>...]
DESCRIPTION
-----------
'git difftool' is a Git command that allows you to compare and edit files
between revisions using common diff tools. 'git difftool' is a frontend
to 'git diff' and accepts the same options and arguments. See
linkgit:git-diff[1].
OPTIONS
-------
-d::
--dir-diff::
Copy the modified files to a temporary location and perform
a directory diff on them. This mode never prompts before
launching the diff tool.
-y::
--no-prompt::
Do not prompt before launching a diff tool.
--prompt::
Prompt before each invocation of the diff tool.
This is the default behaviour; the option is provided to
override any configuration settings.
--rotate-to=<file>::
Start showing the diff for the given path,
the paths before it will move to end and output.
--skip-to=<file>::
Start showing the diff for the given path, skipping all
the paths before it.
-t <tool>::
--tool=<tool>::
Use the diff tool specified by <tool>. Valid values include
emerge, kompare, meld, and vimdiff. Run `git difftool --tool-help`
for the list of valid <tool> settings.
+
If a diff tool is not specified, 'git difftool'
will use the configuration variable `diff.tool`. If the
configuration variable `diff.tool` is not set, 'git difftool'
will pick a suitable default.
+
You can explicitly provide a full path to the tool by setting the
configuration variable `difftool.<tool>.path`. For example, you
can configure the absolute path to kdiff3 by setting
`difftool.kdiff3.path`. Otherwise, 'git difftool' assumes the
tool is available in PATH.
+
Instead of running one of the known diff tools,
'git difftool' can be customized to run an alternative program
by specifying the command line to invoke in a configuration
variable `difftool.<tool>.cmd`.
+
When 'git difftool' is invoked with this tool (either through the
`-t` or `--tool` option or the `diff.tool` configuration variable)
the configured command line will be invoked with the following
variables available: `$LOCAL` is set to the name of the temporary
file containing the contents of the diff pre-image and `$REMOTE`
is set to the name of the temporary file containing the contents
of the diff post-image. `$MERGED` is the name of the file which is
being compared. `$BASE` is provided for compatibility
with custom merge tool commands and has the same value as `$MERGED`.
--tool-help::
Print a list of diff tools that may be used with `--tool`.
--[no-]symlinks::
'git difftool''s default behavior is create symlinks to the
working tree when run in `--dir-diff` mode and the right-hand
side of the comparison yields the same content as the file in
the working tree.
+
Specifying `--no-symlinks` instructs 'git difftool' to create copies
instead. `--no-symlinks` is the default on Windows.
-x <command>::
--extcmd=<command>::
Specify a custom command for viewing diffs.
'git-difftool' ignores the configured defaults and runs
`$command $LOCAL $REMOTE` when this option is specified.
Additionally, `$BASE` is set in the environment.
-g::
--[no-]gui::
When 'git-difftool' is invoked with the `-g` or `--gui` option
the default diff tool will be read from the configured
`diff.guitool` variable instead of `diff.tool`. This may be
selected automatically using the configuration variable
`difftool.guiDefault`. The `--no-gui` option can be used to
override these settings. If `diff.guitool` is not set, we will
fallback in the order of `merge.guitool`, `diff.tool`,
`merge.tool` until a tool is found.
--[no-]trust-exit-code::
'git-difftool' invokes a diff tool individually on each file.
Errors reported by the diff tool are ignored by default.
Use `--trust-exit-code` to make 'git-difftool' exit when an
invoked diff tool returns a non-zero exit code.
+
'git-difftool' will forward the exit code of the invoked tool when
`--trust-exit-code` is used.
See linkgit:git-diff[1] for the full list of supported options.
CONFIGURATION
-------------
'git difftool' falls back to 'git mergetool' config variables when the
difftool equivalents have not been defined.
include::includes/cmd-config-section-rest.txt[]
include::config/difftool.txt[]
SEE ALSO
--------
linkgit:git-diff[1]::
Show changes between commits, commit and working tree, etc
linkgit:git-mergetool[1]::
Run merge conflict resolution tools to resolve merge conflicts
linkgit:git-config[1]::
Get and set repository or global options
GIT
---
Part of the linkgit:git[1] suite